When the tutorial first initializes, the crystal is positioned in an East-West direction with respect to the long axis of the crystal and is almost invisible in crossed polarized illumination. Use the Stage Rotation Angle slider to rotate the crystal through a full 360-degree rotation of the microscope stage. When the crystal is oriented at 45-degree angles to the long crosshairs, it is at maximum brightness. A virtual full-wave retardation plate can be inserted (with radio buttons) between the specimen and the analyzer to measure birefringence of the crystal.